Help! How do I best foul-up my LPG/CNG gas conversion?

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CNG
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Help! How do I best foul-up my LPG/CNG gas conversion?

#1 Post by CNG » Sat Jul 18, 2020 10:26 am

Help! How do I best foul-up my LPG/CNG gas conversion?

As I read the various guides on LPG, a common theme appears. "Which is the best system?", er... "Does this work with my car?" etc etc. I'm bored.

What's needed is a guide for a better class of lash-up.
I've seen more than a few LPG conversions. Among these I've seen sterling effort, the one I've got before me counted 42 Scotchloks, a gauge that doesn't work, and two leaks that do. This conversion must have been done in under three hours. This fitment leaves me in awe; if I'd produced this pile of magnificence it wouldn't work, but nay, this thing runs.

We've all read the Tooless thread:
viewtopic.php?f=33&t=8148

LPG conversions have double-standards to keep. How do we produce something with potential to take streets out? There's folks following an installer guide that's not been written. It's about time. I'll kick-off...
Last edited by CNG on Sat Jul 18, 2020 10:36 am, edited 2 times in total.

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Re: Help: How do I best foul-up my LPG/CNG gas conversion?

#2 Post by CNG » Sat Jul 18, 2020 10:30 am

1) Premises: A railway arch is good.
2) A soldering-iron is bad.

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#3 Post by LPGC » Sat Jul 18, 2020 5:32 pm

I'd suggest a few words for page 1 of any guide - 'This guide assumes you can solder, make joints that don't leak and know how to use nuts and bolts, if you don't then you'll need to read books on those subjects and practice before reading this book'.

Assuming the reader can solder and connect stuff together the rest of the guide could be dedicated to the more tech aspects of LPG conversion, at least in as much detail as the author cares to go into or knows. I wouldn't want to hold my breath waiting for a very comprehensive guide to be written!

If an expert writes a basic guide covering only the basics there will be readers who think the guide is comprehensive, and having read it and understood it think they're now an expert themselves.
Who says the expert is an expert... If someone writes what they think is a comprehensive guide it might seem to cover only the basics to someone more expert, might even seem to have got some of the basics wrong.

I seldom see Scotchlocks or tanks / reducers hanging loose but I see a lot of installs that are poor because the installer didn't address tech aspects properly. An install can be neat and tidy with properly soldered connections, tanks and reducers etc bolted in properly but if it doesn't work as well as it could/should because the installer didn't properly address a tech aspect it's still a poor install.
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#4 Post by Gilbertd » Sat Jul 18, 2020 6:19 pm

Looks like Simon beat me to it. Rather than being bad, a soldering iron, and the ability to use it, is mandatory, along with glue lined heat shrink tubing.

It isn't so much how to do it as understanding how it works so you know why you are doing what you are doing.
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#5 Post by CNG » Sun Jul 19, 2020 7:52 pm

The all-encompassing foul-up guide may never be written, yet looking at the 'effort' i see before me, someone's fully conversant in its contents. Will post pix.

3) Every hose, pipe or wire, cut so tight we're set for a sing-song.

Glue-lined heat shrink tubing? You're having a laugh...

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#6 Post by Budgetbond » Sun Jul 19, 2020 8:51 pm

What an appropriately timed post, feast your eyes on my recent 'creation' unfortunately I didn't have the luxury of a railway arch to complete it!!

But it's actually my finest and unprecedented mechanical achievement and amazingly runs quite well!!!

4) Wholesale spaghetti junction use of cable ties perhaps!!!

Feel free to critique for improvement s.

I wouldve actually liked my injector hoses to perhaps have been at least an inch shorter, but they were fitted and the rubber is quite difficult to manipulate and I'll probably leave it as is for now instead of redoing the work.
However the extremely close long nozzles mean the injection point must be extremely close to the petrol.

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#7 Post by Budgetbond » Sun Jul 19, 2020 8:53 pm

Any suggestions?
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#8 Post by Budgetbond » Sun Jul 19, 2020 8:56 pm

One more more cable tie maybe!!!

:( :shock: :lol:
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#9 Post by Budgetbond » Sun Jul 19, 2020 8:57 pm

Toolless eat your heart out!!!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#10 Post by Budgetbond » Sun Jul 19, 2020 9:12 pm

Have to agree with 2) wish I'd taken a longer crash course in soldering and a better soldering iron than my Chinese gas one!!
Hopefully my connection s and soldering in the field are substantial enough longish term def o wouldn't want to have to repeat it wouldve luv d the luxury of a railway arch!!

5) Don't do this at home perhaps!!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#11 Post by Gilbertd » Sun Jul 19, 2020 10:06 pm

When you said you were going to tidy up the install a bit, I didn't realise that would involve removing it and starting again.......
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Budgetbond
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#12 Post by Budgetbond » Sun Jul 19, 2020 10:19 pm

I know lol, the time I've consumed in having to remediate things and fix things that have arisen at the sametime, I think I prolly will have to take it off and do it again now, but on another car.
Maybe better next time it's been a trusty guinea pig tho!!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#13 Post by Brian_H » Mon Jul 20, 2020 12:07 am

Ideally you want the ecu with the connector facing downwards, It also looks very close to the engine, though that may just be the photo causing that to look like its the case.

Newer ECUs tend to be a lot smaller than that one, and far easier to find a place to install them.

I'm not sure the colour of your cable wrap helps either being cyan!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#14 Post by Budgetbond » Mon Jul 20, 2020 1:11 am

Cheers Brian yeah the ecu s not ideal at the min, I might change it in due course/wrap it in polythene but it's not foulling anything at the min.

And was that a tip no. 6) one more cable tie etc, but in the right colour?!!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#15 Post by Brian_H » Mon Jul 20, 2020 1:36 am

I wouldn't wrap it, as it is designed to be installed like that. Just the connector on the bottom means the seals work to keep water out etc.

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#16 Post by LPGC » Mon Jul 20, 2020 12:42 pm

I've seen far worse! Sometimes it would be far easier to get neat results at the expense of siting components such as manifold nozzles in a less technically ideal position but then the system wouldn't function as well (this links to a point I made in a post above). Tbh if this came in to me I'd presume an amateur had fitted it but at least an amateur who'd acknowledged advice on spud position and intended on good drive-ability results, there are telltales... Even pros who aren't very good and who intend on doing a quick job are still familiar with components they fit and more confident of fitting them and making joints (pipes and electrical) not all within quite so easy reach and not all immediately in front of their eyes. Only an amateur would fit the OTT corrugation around the rpm wire joint, even if a pro had fitted the rest of it I'd know an amateur had 'improved' it! Reducer/ECU are fitted to existing bolt/existing bracket, which can make sense if bolt/bracket are in a good position for using or can imply not so much thought went in or a quick job was intended. Quick improvements now could be to move the ECU and fit a shorter gas filter so you can run a bit longer pipe between reducer and input to filter, or move the filter higher up the pipe to allow a gentler bend on the pipe as it leaves the reducer, pipe from reducer to filter has a slight kink? There would be lots of scope for Improving tidyness even using the components you have or could make for a system where components aren't seen or install is very tidy if some components were changed. Don't get me wrong, I don't think it's any more important for an LPG installer to e.g. hide a reducer than it is for a car designer to e.g. hide an alternator... but alternators are always mounted tidily.
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#17 Post by Budgetbond » Mon Jul 20, 2020 1:22 pm

Yeah I'll try and think of another way of preventing that.

My original intention was to attempt to get my gas hoses really short, I had a plan of how to mount/site them but even attaching the pipes and trying to get them shortish proved difficult with the older rubber, I could probably try and chop another inch + off them, are there any or are new rubber hoses more softer/flexible available?

As a precautionary tale to the uninitiated attempting the task here's a not completely exhaustive list of other things I've had to complete whilst completing and testing this build.

Power steering hose leak and corroded pipe whilst trying to fit and site reducer + ecu.

Front bumper coming off it's nuts/clips also. (Attempted mounting and testing)

Rear bumper coming off it's clips/nuts twice whilst mounting and testing and valance fitted underneath cracking mounting the filler pipe and testing.

Whilst initially trying to fit injector nozzle adaptor s and swapping petrol injectors, eventually had to get a new set of petrol injectors/ pro cleaned as my 2 spare sets I attempted to clean myself whilst off the car and must have 'cocked them up' leading to multiple cylinder misfires dumping loads and loads of unburnt fuel into the cat and exhaust and probably damaging it irreversibly whilst also trying to achieve a necessary upper cylinder/valve/piston clean/soak,thus countless times changing injectors and getting through countless injector seals and orings and trying to eradicate leaks, all attempting not to have to drill the manifold!!

Bleeding the coolant notorious on my car led to v long elevated engine temps risking head and engine damage only minimised by having had to complete the task twice previously.

Using quite a lot of engine oil also during the above unrealized and again risking engine damage notorious on my car.

Anyway apols for the diatrabe hope it's keeping you entertained.

But in answer to the above OP's question are there any other common mistakes/ 'do not's' that are made during installations?

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#18 Post by Budgetbond » Mon Jul 20, 2020 1:52 pm

Oh sorry Simon are replies just 'crossed in the post' there.

Thanks for that, from someone like you, I'll take that as an overall compliment, thanks v much, and thanks a lot for the suggestions.

Yeah, I was maybe thinking of trying to improve gas flow further, and well spotted on that kink I hadn't noticed that, that's what I was maybe going to have a play with.I
Am I right in thinking, like you've said, that it's beneficial generally to have the gas filter fitted closer to the fuel rail?

And yeah, you're right there the rpm signals a bit of a sore thumb lol, I had a load of sheathi ng somebody had given me I thought I mite as well use it.

You can't see but the maps connected to a pre installed now unused butterfly chamber nozzle and I don't know whether that will affect readings at higher/lower revs as it might come from a separate plenum near the throttle body I don't know yet, but I've tried to keep my map pipes as short as poss too, I don't know whether that makes any difference too?


I tried to make it easy, using what id got but still generally trying to comply with all the cop11 regs.

Mounting of pipes and heat from the engine's also a bit confusing, I've tried to keep the heat to the gas up post reducer but minimise it mostly pre reducer but also trying to achieve quick 'warm-up' times but keep temp. stability.

(Oh and yeah also to the uninitiated the complications in getting, choosing and fitting, leak-free of the right connections, I've still got a bag of the wrong one's!! Oh and hoses too!!!

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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#19 Post by LPGC » Mon Jul 20, 2020 3:38 pm

If you mean the throttle butterfly the manifold pressure signal might not be right in which case you might want to fit a vacuum take-off a bit further into the manifold.

Wouldn't worry much where in the pipe the filter is but if anything it's probably better closer to injectors. There isn't much in it but since moving the filter further up the pipe should also remove the kink you might as well do that.

As long as the reducer is plumbed to hot water properly there isn't much point trying to manipulate gas temperature at the injectors by altering pipe lengths etc, the vapour moves pretty quick through the main feed pipe and won't have much chance to be warmed/cooled before it reaches injectors.. and anyway a couple of degrees either way wouldn't effect performance. You wouldn't run a long gas pipe touching the radiator or in a position where it would be open to windchill but other than such extremes (which you'd never need do) you're not going to affect gas temp at the injectors much. You obviously wouldn't want any pipe to be close to extreme heat sources such as the exhaust especially if it's a type of pipe that could burn, copper less susceptible than plastic or rubber except if the copper has protective plastic cover. Water pipe length isn't as critical as where they're connected and how they are routed (air locks, dips and peaks relative to the engine / heater circuit / header tank / rest of the cooling system). Short pipes have potential to be neater than longer pipes, a short pipe is less stuff than a long pipe... but a nicely routed long pipe is neater than a poorly routed short pipe. From a tech point of view gas pipe length is more about pressure aspects than temperature aspects but again there's little point worrying about an inch difference in the pipe between reducer and injectors.

On aircooled engines the reducer cannot be heated by engine coolant/water because the engine doesn't have any coolant/water, so gas from the tank is preheated before it reaches the reducer using a heat exchanger fitted inside the exhaust... But you wouldn't want to try to emulate that without using the special heat exchanger and you wouldn't want to do it at all on a liquid cooled engine.
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Re: Help! How do I best foul-up my LPG/CNG gas conversion?

#20 Post by Budgetbond » Tue Jul 21, 2020 12:36 am

Thanks vv much Simon, you're a hero, I share your enthusiasm for what you do, if not your technical wizardry.

I've slightly smoothed out my pipework today and yes taken out that kink a bit and removed the spoiling 'cyan' cable tie!!

The only issue I have pipework wise I don't know whether you can notice from the pics is, that the fuel pipe to the reducer slightly caresses some of the coolant and throttle body coolant hoses, runs slightly alongside the engine and goes behind the coolant reservoir along the top of the rad a bit?
And is thus on a slightly longer path.
I knew this at the time I ran and connected it for securities said I didn't know where some of my electrical cables would lie.
Any ramifications of this path at all, I may shield it or indeed move and shorten it in due course.

My map hose is connected to an existing vac pipe outlet on the manifold that should operate a 'butterfly' resonator type valve in the original air filter box, it's just after the throttle body but may be in a separate plenum (for running at low revs possibly?)
Any opinions on if that's a bad location for it?

Thanks for all your v useful comments, but today, aptly for this thread, on my first long journey coming back I got quite a big misfire and stuttering, both on petrol and lpg, and had to limp home, no leaks as far as I can tell, and although it's running rich and needs recalibrating I suspect my soldering wasn't up to scratch on my injector connections, as in the above point's, but I also suspect my vvti solenoid/filter due to other issues arisen, anyway I'll investigate a bit more tommorrow and report back on my thread, thanks.

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